An automatic testing machine (ATM) operates in a production environment to rapidly and accurately test the operation and performance of various types of devices under test (DUT), including RF communication devices. The DUTs could be a finished product or a component of a larger system.
The ATM is programmed to perform various tests on the DUT automatically. For example, RF signals are transmitted to a finished cellular telephone DUT to determine if the telephone activates. Other tests could include environmental tests, such as temperature or vibration tests.
Depending upon the nature and number of the tests being performed, the testing may last from a couple of milliseconds to several minutes. The information from the testing is compared with expected test results. If there is some defect so that the DUT falls below specifications, the ATM will designate the DUT as failed, either by marking the DUT, placing the DUT in a failure area, or indicating the failure to an operator.
The ATM is then loaded with the next DUT, either manually or automatically, and the testing procedure is repeated for this DUT. The information from the testing can be used to evaluate the fabrication process for possible changes, as well as to perform failure analysis on individual failed devices.
Typically, each ATM is designed to perform a specific class of tests on the DUT, and are not able to perform other classes of tests. For example, a vibration ATM may not be able to perform electrical signal tests. However, different types of DUTs may require the same tests to be performed. For example, all types of microcomputer chips are tested for electronic performance characteristics, but different chips will have different locations for power, inputs and outputs. ATMs are made flexible by the use of test fixtures. The test fixture provides an interface between the device under test DUT and the ATM. Thus, a single ATM can perform tests on different types of devices when connected via different fixtures.
A particular class of fixtures are RF fixtures. RF fixtures are used in the testing of DUTs that operate with radio waves, e.g. cellular telephones, pagers, CB radios, etc. The RF fixture is sealed such that external electromagnetic fields or radio waves do not affect the testing of the DUT. Thus, the RF testing being performed on the DUT will be performed accurately, as the DUT will receive only the test RF signals and not any external RF signals which may skew the operation of the DUT. The RF seal is critical to ensure proper testing of the DUT. If the RF seal should leak, external RF signal could enter the test fixture and interfere with RF testing of the DUT, resulting in the collection of incorrect information about the DUT. The incorrect information could lead to improperly passing a defective DUT or failing a passing DUT. The incorrect information may also result in incorrect or unnecessary changes being made to the production process.
The RF sealing requirements make it difficult for RF fixtures to be properly constructed. A large number of screws are used to secure the sides of the RF fixture cabinet. Gaskets may be used to seal the panels. For example, as shown in FIG. 3, 28 screws 33 are used to secure right side panel 32 of fixture 31 to top side panel 34, and 28 screws 33 are used to secure front side panel 35 to top side panel 34, right side panel 32, left side panel (not shown), and bottom side panel (not shown). Similar amounts of screws would be used to secure the right side panel (not shown) and the back side panel (not shown) for a total of 112 screws 33. The number and location of the screws is by way of example only, as the precise number and placement depends upon the size and shape of the fixture, with the main consideration being to provide a proper RF seal.
The large number of screws causes the fabrication process of the fixtures to be very time consuming. Each screw must be precisely placed and properly tightened. If the screw is too loose then the seal at that particular location is poor. If the screw is too tight, then this may cause the side panel to buckle and result in a poor seal. Furthermore, a screw that is too tight may strip and thus result in a poor seal at that location. Also, a screw that is overly tightened may result in a stripped or broken screw head, which must be drilled out and replaced or a poor seal will result at that location. Frequently, during fabrication of the RF fixture, many of the screws are not installed, thus leaving the fixture susceptible to RF interference.
Maintenance of the RF fixture is also a problem. To service the internal elements of the RF fixture at least one side needs to be opened, thus each screw around the periphery must be removed in order to remove the side. For example, as shown in FIG. 3, in order to remove right side 32, each of row of screws 33 on the top and bottom portions of right side 32 must be removed. Moreover, the right side column of screws 33 of both front side 35 and rear side (not shown) must also be removed in order to remove right side 32, yielding a total of 44 screws that must be removed. In addition, more than one side panel typically needs to be removed to service the fixture. And frequently, after the maintenance of the RF fixture has been completed, not all of the screws are re-installed, thus leaving the fixture susceptible to RF interference. Also, if the screws are replaced, the fabrication problems resulting from under and over tightening may occur during maintenance. Furthermore, during maintenance of the fixture, the production line may be shut down if a replacement fixture is not available, which results in lost production time. Thus, the time required to open and close a RF fixture can greatly affect production.
Therefore, there is a need in the art for a system and method that allows for the rapid and reliable installation of RF sealed fixture side panels.